Temporal dependence of high-order harmonics in the presence of strong ionization

Abstract : The temporal behavior of the 19th harmonic of a Ti:sapphire laser generated in argon was investigated by a cross-correlation technique at intensities close to saturation. Pulses about half as long as predicted on the basis of the scaling law of the atomic dipole strength on intensity were found. Analysis shows that this is a consequence of both the intensity-dependent dipole phase and the depletion of the medium by ionization.